Next story in Space

A photo made from NASA video shows the Endeavour docked on the Harmony node of the International Space Station, Wednesday May 18, 2011 on the penultimate voyage of the space shuttle program. It is carrying a particle physics detector for the station. (AP Photo/NASA)

Science editor Alan Boyle's blog: "Astronaut Abby" is at the controls of a social-media machine that is launching the 15-year-old from Minnesota to Kazakhstan this month for the liftoff of the International Space Station's next crew.

It took the crews on both the station and shuttle another two hours to check for leaks in the seal between their two spacecraft. Then the doors were opened and the shuttle astronauts floated through.

"Hey, you guys wore coordinating shirts. We didn't do that," shuttle commander Mark Kelly said as he climbed aboard the space station. "It's good to be back. It looks pretty much the same."

Kelly last saw the International Space Station in 2008 during his STS-124 shuttle mission. During Wednesday's greetings, he and the other spacefliers welcomed each other with hugs and handshakes.

Endeavour made its last liftoff Monday morning, beginning a 16-day mission to orbit. The shuttle will stay at the space station until May 29, when it will undock to begin the trek back to Earth for good. [Photos of Shuttle Endeavour's Final Launch]

Their addition to the space station doubles the outpost's population. Currently living aboard the station with Nespoli as part of the Expedition 27 mission are commander Dmitri Kondratyev of Russia, and flight engineers Ron Garan and Catherine Coleman of NASA, and Russian cosmonauts Alexander Samokutyaev and Andrey Borisenko.

The station residents were excited to have visitors.

"Yoo Hoo house-guests!" Garan wrote via Twitter on Tuesday.

Busy mission
The main goal of Endeavour's final mission is to deliver an astrophysics experiment called the Alpha Magnetic Spectrometer to the International Space Station. At $2 billion, it's the most expensive science experiment ever flown to the station, and offers the potential to solve numerous cosmic mysteries, such as what constitutes the invisible dark matter thought to pervade the universe.

NASA TV

The space shuttle Endeavour approaches the International Space Station shortly before Wednesday's docking.

Endeavour is also packed with spare supplies for the space station, including extra ammonia coolant, antenna systems and parts for the station's Dextre robot.

The shuttle's crew plans four busy spacewalks and a host of intensive robotic arm maneuvers to stow the parts and perform maintenance on the exterior of the station.

The graveyard shift
Endeavour's astronauts are working the overnight shift during their mission, relative to Mission Control time in Houston.

The crew woke Tuesday evening at 10:56 p.m. ET to the song "Drops of Jupiter" by the band Train. The tune was selected for Johnson by his family and radioed up to the shuttle by Mission Control.

"I love that song and I love being in space," Johnson said. He thanked his teenage son Matt for the choice, and apologized for missing his birthday, which is Thursday. "And I want to say that's a perfect way to start an exciting rendezvous day!"

"Preliminary assessment is it looks really good so far," LeRoy Cain, head of Endeavour's mission management team, said during a news briefing Tuesday. "We're not tracking any issues as far as that's concerned."

Another check of the heat shield will be available soon, when Mission Control has a chance to analyze high-resolution photos taken of the shuttle's underbelly as it approached the station.

When Endeavour was about 600 feet (180 meters) below the space station, Kelly steered the shuttle through a backflip that exposed the orbiter's heat shield to the station, allowing astronauts there to snap hundreds of detailed images. The operation is called the Rendezvous Pitch Maneuver.

Special delivery

Endeavour was the last space shuttle to join NASA's fleet: It was built to replace the shuttle Challenger, which was lost in an explosion shortly after launch in 1986. This view shows Endeavour perched atop a modified Boeing 747 on May 2, 1991, beginning the ferry flight from Palmdale, Calif. - where the shuttle was built - to Kennedy Space Center in Florida.
(NASA)
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First liftoff

Endeavour lifts off from Launch Pad 39B at NASA's Kennedy Space Center on May 7, 1992, beginning its first mission. The STS-49 mission's primary task was the repair of the Intelsat VI telecommunications satellite. Endeavour was the only shuttle to make its maiden flight from Pad 39B.
(NASA)
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Grab that satellite!

Endeavour astronauts Richard Hieb, Thomas Akers and Pierre Thuot hold onto the 4.5-ton Intelsat VI satellite after making a six-handed "capture" on May 13, 1992. The satellite failed to rise above low Earth orbit when it was launched in 1990. During Endeavour's maiden mission, astronauts retrieved the satellite, attached it to a new upper-stage booster and relaunched it to its intended geosynchronous orbit. This mission marked the first time that three people from the same spacecraft walked in space at the same time.
(NASA)
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Science in space

Endeavour astronauts Jan Davis, left, and Mae Jemison prepare to deploy the lower body negative pressure apparatus on Sept. 15, 1992. Scientific research was the main focus of this Spacelab-J mission, also known as STS-47. The mission's crew included the first African-American woman to fly in space (Mae Jemison) and the only husband-and-wife team to go into space together (Jan Davis and Mark Lee).
(NASA)
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Fixing Hubble

Astronauts flew on Endeavour to take on the first Hubble servicing mission in December 1993. In this picture, spacewalkers Story Musgrave and Jeffrey Hoffman perform an orbital ballet. The coastline of western Australia is visible below. The complex and highly successful repair mission allowed Hubble, which was launched with a defective mirror, to see into the universe with unprecedented clarity.
(NASA)
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Erroneous endeavor

The shuttle Endeavour sits on its launch pad at Kennedy Space Center in Florida on July 11, 2007. "Endeavor" is spelled incorrectly on the banner. The shuttle was named after the HMS Endeavour, the British sailing ship that carried Captain James Cook on his first voyage of discovery from 1768 to 1771. That's why Endeavour reflects the British spelling of the word.
(Eliot J. Schechter / Getty Images)
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Spacewalkers at work

During the first spacewalk of the STS-118 mission, on Aug. 11, 2007, astronaut Rick Mastracchio and Canada's Dave Williams (out of frame) attach a new segment of the International Space Station's truss and retract a collapsible radiator.
(NASA)
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Class portrait

The crew members of Endeavour's STS-118 crew pose for their official portrait on Aug. 8, 2007. From left are Rick Mastracchio, Barbara Morgan, pilot Charles Hobaugh, mission commander Scott Kelly, Tracy Caldwell, Canadian astronaut Dave Williams and Alvin Drew. During this flight, Morgan became the first educator astronaut to go into orbit. In 1986, she was the backup for Christa McAuliffe, the New Hampshire teacher who died in the Challenger explosion.
(NASA)
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Great view

Endeavour spacewalker Rick Mastracchio relocates communications equipment on the International Space Station during an outing on Aug. 15, 2007.
(NASA)
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A gouge in the tiles

Tiles on the underside of the space shuttle Endeavour show evidence of damage in a photo taken on Aug. 12, 2007, using the shuttle's robotic arm and a camera-tipped extension boom. The close-up imagery helped mission managers determine that the gouge would pose no threat during Endeavour's atmospheric re-entry.
(NASA via AP)
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Eye of the hurricane

Crew members aboard the shuttle Endeavour captured this picture of Hurricane Dean's eye in the Caribbean on Aug. 18, 2007. The STS-118 mission ended on Aug. 21, one day earlier than planned, to avoid potential complications due to the storm. Forecasters worried that Hurricane Dean could have swept over Houston around the time of landing - but in the end, the storm took a different course.
(NASA)
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In control

NASA Administrator Michael Griffin watches the liftoff of the space shuttle Endeavour from the Launch Control Center at NASA's Kennedy Space Center on Nov. 14, 2008. The STS-126 mission delivered two spare bedrooms as well as a second kitchen and bathroom to the International Space Station.
(Bill Ingalls / NASA)
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Repairs at the pad

Workers perform repairs on the shuttle Endeavour's external fuel tank at the Kennedy Space Center launch pad on June 14, 2009. The launch team detected a leak of hydrogen fuel from the tank, forcing a delay in Endeavour's STS-127 launch. The mission's main task was the delivery of the final segment of Japan's Kibo laboratory to the International Space Station.
(Tim Jacobs / NASA)
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Liftoff at last!

Parting glance

The space shuttle Endeavour is photographed from the International Space Station soon after its departure on July 28, 2009. A Soyuz spacecraft docked at the station is visible in the foreground.
(NASA)
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Twilight of the shuttle

The shuttle Endeavour is silhouetted against different layers of the sunlit atmosphere during its approach to the International Space Station on Feb. 9, 2010. The primary payloads for Endeavour's STS-130 mission were the Tranquility module and the Cupola observation deck and control station.
(NASA)
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Tanks for the memories

The external fuel tank for Endeavour's final mission, STS-134, is transported to the Vehicle Assembly Building at the Kennedy Space Center in Florida on July 14, 2010. STS-134's main payload is the $2 billion Alpha Magnetic Spectrometer, an international physics experiment.
(John Raoux / AP)
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The view from above

The space shuttle Endeavour is lowered into place for attachment to its external fuel tank and solid rocket boosters in the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida on March 1, 2011.
(NASA via Getty Images)
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Godspeed, Endeavour!

Spectators react as the space shuttle Endeavour lifts off from NASA's Kennedy Space Center in Florida on May 16. Hundreds of thousands of people watched the start of the next-to-last space shuttle flight.
(Scott Audette / Reuters)
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Above the clouds

Stefanie Gordon captured this remarkable picture of the space shuttle Endeavour rising above Florida's cloud cover on May 16 while she was on a commercial flight from New York to Palm Beach, Fla.
(Stefanie Gordon / for msnbc.com)
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The last spacewalk

NASA astronaut Greg Chamitoff holds a handrail during the fourth and last spacewalk conducted by the shuttle Endeavour's crew at the International Space Station on May 27. Chamitoff and astronaut Michael Fincke (visible in the reflections from Chamitoff's helmet visor) transferred an inspection boom system, completing U.S. assembly of the station. The May 27 outing marked the last scheduled spacewalk to be conducted by a space shuttle crew.
(Nasa T.V. via EPA)
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Night passage

Backdropped by a nighttime view of Earth and the starry sky, the space shuttle Endeavour is seen docked to the International Space Station on May 28.
(NASA via Reuters)
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Landing in the dark

The space shuttle Endeavour lands for the last time at NASA's Kennedy Space Center in Florida on June 1, 2011. The touchdown capped Endeavour's 16-day mission to deliver a $2 billion science experiment to the International Space Station on NASA's next-to-last shuttle flight.
(Joe Skipper / Reuters)
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Blastoff into history

A NASA poster pays tribute to Endeavour and its space missions over the past two decades. The shuttle is shown rising to orbit, with patches for each of its missions laid out in a spiral. The HMS Endeavour, which inspired the spaceship's name, is shown at lower right. At upper left, pictures of Endeavour are framed in the windows of the Cupola. The background image depicts the nebula NGC 602 as seen by the Hubble Space Telescope, which was first serviced by Endeavour in 1993.
(NASA)
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Editor's note:
This image contains graphic content that some viewers may find disturbing.